"With health concerns I am super careful with what I have been doing and everyone in the Serena bubble is really protected.
"It is cool to play tennis, but this is my life and my health, so I have been a little bit neurotic but that is how I have to be right now."
Williams revealed that she had been practicing on her own court, built with the same hardcout surface used at the US Open. She has also stayed fit with construction of a home gym.
"I had to make a gym and my husband made a court for me. The gym is not quite done. The tennis court is fun, I go there and it is my own sanctuary. It's like, 'Why haven't I done this 20 years ago?'," she said.
Williams, who is also scheduled to play the Western and Southern Open tune-up event in New York before the US Open, admitted that only tournament play would allow her to properly gauge her fitness.
"Everyone has an opportunity to be more fit now, because we spent so much time at home to work on ourselves," Williams said.
"Fitness wise, there is going to be a tonne of fitness, but match fitness is different to fit-fitness."
Williams, who turns 39 in September, meanwhile said she was unable to say whether she would be at the rescheduled Tokyo Olympics in 2021.
"That is just looking too far ahead, I don't know if Tokyo plans to be in Tokyo, we will have to wait and see," she said.
"I don't know what to expect. One thing I have learned is don't plan, I am living for the day and for the moment, in a good way but I am not making plans too far out."